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  • #46
    Originally posted by Evan View Post
    Think.
    I am not interested in thinking about what you have to say. See post 34.

    I read Stick and Rudder.

    I have done takeoff, departure, ordinary, accelerated, a stall under "the hood" and even an unplanned secondary stall.

    This also included practicing adding full power and establishing a climb attitude so as to minimize altitude loss.

    If the fundamentals differ by aircraft let me know, but at roughly 16 degrees AOA a 172 let's go (so I've read).

    What I have not_read, but instead, lived: there is a thump, the nose falls and often, some nose-down input is used (with diligence to keep the input appropriate and adequate).


    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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    • #47
      Originally posted by 3WE View Post

      Indeed, you are incapable of saying that you can add power and avert a stall...You always have to say 10X more stuff because somehow (in your mind), no one knows that a stall is a loss of lift from bad airflow when the critical AOA is exceeded.
      You you can add power and avert a stall (there you have). No problem.

      Just it is not a causal relationship. Adding power doesn't by itself cause a stall to be averted.

      You can also scratch your ear and avert a stall.

      Adding power has everything to do with not losing altitude during the recovery. You do have a causal relationship there.

      --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
      --- Defend what you say with arguments, not by imposing your credentials ---

      Comment


      • #48
        Originally posted by Gabriel View Post

        I never said "lower the nose". I never said "loss of altitude".
        In fact I said "reduce AoA" and I also said "AoA can be reduced while at the same time increasing pitch, climb rate and flight path angle".
        Aknowledged. However, maybe it would help if you just came out and said it: how do you lower AoA without lowering pitch?

        EDIT: nevermind, I see you just came out and said it in the previous post.
        EDIT: no, wait, you didn't, really...

        Causal relationship: Power causes airspeed to increase / which causes an increase in lift / which causes a reduction in the angle between the wing chord and the flight path / an angle known as the angle of attack.

        Comment


        • #49
          Originally posted by Evan View Post

          Aknowledged. However, maybe it would help if you just came out and said it: how do you lower AoA without lowering pitch?

          EDIT: nevermind, I see you just came out and said it in the previous post.
          EDIT: no, wait, you didn't, really...
          Quting myself in #19:

          I've said it before: It is possible to reduce the AoA and, at the same time, increase the speed, the vertical speed, the pitch and the flight path slope. You just need that the flight path increases more than the pitch and that's a reduction of AoA by definition (because AoA is pitch - flight path slope).
          Causual relationship: Power causes airspeed to increase / which causes an increase in lift / which causes a reduction in the angle between the wing chord and the flight path / an angle known as the angle of attack.
          #19 again. This time I will re-explain instead of quoting myself.

          That is not how it works. The reduction in AoA due to the increase in wing lift is minimal and very short-lived because the airplanes have a very short short-period mode of longitudinal oscillation, i.e. are very stable around the trim AoA (trim AoA in this context means equilibrium AoA for the current configuration and position of the elevator/stabilizer). So as soon as the plane starts do move up the air will hit the stabilizer more from above and it will pitch up thus keeping the AoA fairly constant, except...

          A longer term (but not sustainable) reduction of AoA will come later when the plane starts pitching up at increasing pitch rates (the pitch rate will be a function between the the current airspeed and the trim airspeed, and since the airspeed is increasing after your application of power the pitch rate will be increasing). When that happens, the stabilizer moves down due to the pitch angular motion and its distance aft of the CG. That downward movement means that the air is now hitting the stabilizer more from below (more and more as the pitch rate increases) which will lower the AoA more and more. However, left alone, you know where this goes. There will be a point where the airplane has pitched up so much that the speed starts to decrease, but the plane is still going too fast so it keeps pitching up. That means that it overshoot the equilibrium point. Eventually the speed will have decayed enough where the airplane stops pitching up. At that point you will be baco with the original AoA (assuming no pitching moments due to thrust). Except that now the plane is pitch too much up and will keep loosing speed. Now the effect reverses: The plane starts pitching down at increased rates, the air starts hitting the elevator more from above, and the plane increases its AoA (while still pitching down) beyond the AoA it had when you added thrust back then. It is called long-period mode of longitudinal oscillation or phugoid. You may have just gone from the onset of the stick-shaker to a fully developed stall (with several seconds of temporaty lower AoA in between).

          So adding thrust(*) initially and simultaneously increases speed, pitch, climb rate and flight path angle while at the same time reducing AoA. It buys you time. But you better quickly start that "some modulation" that you mentioned before to prevent the overshoot. That will have you pushing down pretty strongly (or trimming down quite a bit), and it is THAT what recovers the situation for good.

          (*) Assuming no nasty thrust-induced uncontrollable pitch-up moments.

          --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
          --- Defend what you say with arguments, not by imposing your credentials ---

          Comment


          • #50
            Originally posted by Gabriel View Post
            1. power doesn't by itself cause a stall to be averted.

            2. You can also scratch your ear and avert a stall.

            3. it is not a causal relationship
            1. Let me quote me:

            Originally posted by 3BS
            A.a stall is a loss of lift from bad airflow when the critical AOA is exceeded.
            B.
            at roughly 16 degrees AOA a 172 let's go (so I've read).


            2 & 3. Bullshit. And not just bullshit, REALLY WEEK BULLSHIT.

            Power causes increased speed and increased lift and increased climb which reduces AOA. It CAUSES the recovery (and, yes AOA is reduced in the process because I have 'extensive' PPL training which taught me that)


            Scratch your ear? Scratch my a$$. (Actually I'd prefer you didn't nor would I prefer the more commonly used phrase)



            Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

            Comment


            • #51
              Originally posted by Gabriel View Post

              Quting myself in #19:





              #19 again. This time I will re-explain instead of quoting myself.

              That is not how it works. The reduction in AoA due to the increase in wing lift is minimal and very short-lived because the airplanes have a very short short-period mode of longitudinal oscillation, i.e. are very stable around the trim AoA (trim AoA in this context means equilibrium AoA for the current configuration and position of the elevator/stabilizer). So as soon as the plane starts do move up the air will hit the stabilizer more from above and it will pitch up thus keeping the AoA fairly constant, except...

              A longer term (but not sustainable) reduction of AoA will come later when the plane starts pitching up at increasing pitch rates (the pitch rate will be a function between the the current airspeed and the trim airspeed, and since the airspeed is increasing after your application of power the pitch rate will be increasing). When that happens, the stabilizer moves down due to the pitch angular motion and its distance aft of the CG. That downward movement means that the air is now hitting the stabilizer more from below (more and more as the pitch rate increases) which will lower the AoA more and more. However, left alone, you know where this goes. There will be a point where the airplane has pitched up so much that the speed starts to decrease, but the plane is still going too fast so it keeps pitching up. That means that it overshoot the equilibrium point. Eventually the speed will have decayed enough where the airplane stops pitching up. At that point you will be baco with the original AoA (assuming no pitching moments due to thrust). Except that now the plane is pitch too much up and will keep loosing speed. Now the effect reverses: The plane starts pitching down at increased rates, the air starts hitting the elevator more from above, and the plane increases its AoA (while still pitching down) beyond the AoA it had when you added thrust back then. It is called long-period mode of longitudinal oscillation or phugoid. You may have just gone from the onset of the stick-shaker to a fully developed stall (with several seconds of temporaty lower AoA in between).

              So adding thrust(*) initially and simultaneously increases speed, pitch, climb rate and flight path angle while at the same time reducing AoA. It buys you time. But you better quickly start that "some modulation" that you mentioned before to prevent the overshoot. That will have you pushing down pretty strongly (or trimming down quite a bit), and it is THAT what recovers the situation for good.

              (*) Assuming no nasty thrust-induced uncontrollable pitch-up moments.
              OK, now I feel like you're getting a bit pedantic on me. It's all interesting and I appreciate that edification, but, again, I'm not suggesting that you can take your hands off the yoke/sidestick/broomhandle and just let power do its magic; I'm just suggesting that you can maintain (more or less) the pitch and escape with power. Maintain means to actively control it. With pitch inputs.

              So, what happens if you do that? After scratching my head several times I arrive at the conclusion that the building airspeed will cause the aircraft to rise faster at a given pitch and that will cause the freestream to come at an angle closer to that of the wing chord, and that would be, by definition, a reduction of AoA. How can that not be true?

              Comment


              • #52
                Originally posted by Evan View Post

                OK, now I feel like you're getting a bit pedantic on me. It's all interesting and I appreciate that edification, but, again, I'm not suggesting that you can take your hands off the yoke/sidestick/broomhandle and just let power do it's magic; I'm just suggesting that you can maintain (more or less) the pitch and escape with power. Maintain means to actively control it. With pitch inputs.

                So, what happens if you do that? After scratching my head several times I arrive at the conclusion that the building airspeed will cause the aircraft to rise faster at a given pitch and that will cause the freestream to come at an angle closer to that of the wing chord, and that would be, by definition, a reduction of AoA. How can that not be true?
                You are describing the effects correctly but not the causality. Yes, if you keep the pitch constant while increasing the airspeed the freestream will come at an angle closer to the chord and the AoA will decrease, but I can also say that the AoA will decrease and the freestream will come at an angle closer to the chord. Or I can say that if you increase the flight path and reduce the AoA in the same amount, the pitch remains constant. There is this formula, AoA = pitch - flight path angle, that tells you the relationship between these 3 varaibles, but it says nothing about causality.

                For example, say that you have a car whose wheels have a diameter of 1 m. Would you say that the car moved forward 100 m BECAUSE the wheels spun 100 times? Or is it that the wheels spun 100 times because the car moved forward 100 m? If you asked me, it's neither.

                So, in the example that you gave,we want to see what causes the reduction in AoA. There are 2 actions taken by the pilot: Advance the throttles and, as the speed increases, slowly push down to keep the pitch. Let's say that we plot the throttle position, the elevator position and the AoA over time.

                Ok, advance the throttle exactly in the same way and don't move the elevator. What happens with the AoA? Anything similar to the original plot? No, not at all, not even remotely close.
                Now repeat exactly the same motion with the elevator but don't touch the throttle. What happens with the AoA? It's almost an exact replica of the original plot (but the pitch plot will look completely different).

                It is the motion of the elevator, not the motion of the throttle, which controls the AoA.

                You may say that I am being pedantic. But I truly believe that understanding these things deeply and correctly is very important to be a good pilot beyond being a good procedure follower (which another part of being a good pilot). Being correct for the wrong (or unknown) reasons is just not good enough in my opinion.

                --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                --- Defend what you say with arguments, not by imposing your credentials ---

                Comment


                • #53
                  Originally posted by 3WE View Post
                  Power causes increased speed and increased lift and increased climb which reduces AOA. It CAUSES the recovery (and, yes AOA is reduced in the process because I have 'extensive' PPL training which taught me that)[/SIZE][/FONT][/COLOR]
                  Sorry but no. What you just described would cause the plane to pitch up. It is you preventing the plane from pitching up (by moving the yoke forward, which does not mean pitching down) what reduces the AoA.

                  --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                  --- Defend what you say with arguments, not by imposing your credentials ---

                  Comment


                  • #54
                    Originally posted by Gabriel View Post

                    Sorry but no.
                    Sorry but yes.

                    Quit moving the goalposts..we are averting a stall...piloting involves attitude management. Attitude is affected by many external factors INCLUDING speed changes.

                    Is there any way you can briefly explain what Evan’s not getting or is it simply binary thinking?
                    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                    Comment


                    • #55
                      Originally posted by Gabriel View Post

                      So, in the example that you gave,we want to see what causes the reduction in AoA. There are 2 actions taken by the pilot: Advance the throttles and, as the speed increases, slowly push down to keep the pitch. Let's say that we plot the throttle position, the elevator position and the AoA over time.
                      Let's say that we also plot the altitude (vertical flight path). In this case, it continues to climb sufficiently to avoid those hills coming up.

                      Ok, advance the throttle exactly in the same way and don't move the elevator. What happens with the AoA? Anything similar to the original plot? No, not at all, not even remotely close.
                      It increases (for the reasons you have enumerated) and perhaps results in a stall. We don't want to do that. Why would we do that?

                      Now repeat exactly the same motion with the elevator but don't touch the throttle. What happens with the AoA? It's almost an exact replica of the original plot (but the pitch plot will look completely different).
                      It reduces, but so does the vertical flight path and then we have those hills to deal with. There's not much point in escaping the approach to stall regime if we end up slamming into a hill.

                      It is the motion of the elevator, not the motion of the throttle, which controls the AoA.
                      When altitude is of critical concern, it has to be both. And maintaining or increasing the flight path angle while reducing the AoA is done with power.

                      Yes, elevator control is part of that, but it is still what I think can fairly be called 'powering out' of a stall warning.

                      Again, how is that not so?

                      Comment


                      • #56
                        Originally posted by Evan View Post

                        Let's say that we also plot the altitude (vertical flight path). In this case, it continues to climb sufficiently to avoid those hills coming up.

                        It increases (for the reasons you have enumerated) and perhaps results in a stall. We don't want to do that. Why would we do that?

                        It reduces, but so does the vertical flight path and then we have those hills to deal with. There's not much point in escaping the approach to stall regime if we end up slamming into a hill.

                        When altitude is of critical concern, it has to be both. And maintaining or increasing the flight path angle while reducing the AoA is done with power.
                        Exactly. And you are elevatoring out of the stall and powering out of the ground.

                        Yes, elevator control is part of that, but it is still what I think can fairly be called 'powering out' of a stall warning.
                        Again, how is that not so?
                        Call it power it out of the stall if you want. Call it Charlie.

                        Go tell this Pilatus pilot to power out of the stall or that he did was not very wrong Or Pinnacle four oh' one it. Or AF447. Or Colgan. Or the MD-80 at Detroit. Or Spanair at Madrid.

                        I don''t care what you do with the power, do whatever you need to do with it to minimize the altitude loss if it is worth it (which in 1/2 of the examples above it was not). But whatever you do, you are not going away from the stall until you lower the AoA which almost always includes doing something else other than adding thrust.

                        In my humble but strong opinion, calling it "power it out of the stall" gives the absolutely wrong message. Yes, you can add to that an asterisk and a disclaimer of what you mean.

                        Or you can say: Elevator controls airspeed/AoA, power controls altitude/climb rate.

                        Have to much AoA? Move the elevator forward. Need to climb? Add power. Need to lower the AoA AND climb? Do both.

                        I am out of here.

                        --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                        --- Defend what you say with arguments, not by imposing your credentials ---

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                        • #57
                          Somehow related:

                          https://www.youtube.com/watch?v=m_tKShlf_gU

                          And the comments!

                          I’m upset at the fact that I got my private eight years ago and am learning this now. Easily the greatest aviation lesson I’ve ever had.
                          It was me. It still haunts me. I fly the same situation thousands of times in my head. It was 33 years ago. I was getting ready to head to the airport to fly the PA-12 tow plane for the TG-2, the same sailplane that I learned to fly in and soloed when i was 15. My October FLYING magazine had just arrived. On the cover was a panel heading to an opening in the forest. The title was " You lost your engine. What now hotshot"?

                          The takeoff was short. The climb was steep as usual but with plenty of airspeed. I was already 175 feet, and then the invisible instructor chopped the throttle.

                          I so wish that I had seen this video before that day!

                          The instructors that I had, said to land straight ahead. We did our sudden power loss surprises at low level, but never at 175 feet with the end of the runway, power wires, a deep ditch and a swamp ahead of me. When the engine suddenly stopped, time was wasted in disbelief and checking fuel valve and magneto switch, all things that were already covered in the checklist while safely on the ground. In the seconds wasted, the nose was not dropped and precious MINIMUM MANEUVERING SPEED was violated! I never heard of that, until this video and all of the guys who get paid to fly didn't hesitate with the answer.

                          As speed dropped, I decided the best route was about 45 degrees to the right. Can you guess what happened next? You can't recover from a half spin at 150 feet. I do remember what could have been my last thoughts. "Oh ****, this is going to hurt!"

                          I didn't really learn anything from this video. You see, I have reflown that flight thousands of times. Pretty much every day for the last 33 years.

                          --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                          --- Defend what you say with arguments, not by imposing your credentials ---

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                          • #58
                            I am sure glad I never had any of the three of you as F/O's.

                            Comment


                            • #59
                              Originally posted by Gabriel View Post


                              In my humble but strong opinion, calling it "power it out of the stall" gives the absolutely wrong message.
                              Yes, I think this is why you resist it. I agree, you don't want to imbue pilots with that mentality.

                              BTW, I was responding to 3WE's comment asking if you can EVER power out of a stall. It has nothing to do with this Pilatus crash.

                              In fact it has to do with very rare stall scenarios that occur at critically low altitude during takeoff with high power settings.

                              But whatever you do, you are not going away from the stall until you lower the AoA which almost always includes doing something else other than adding thrust.
                              I never suggested doing nothing other than adding thrust.

                              Or you can say: Elevator controls airspeed/AoA, power controls altitude/climb rate.
                              Or you can say: Climb rate controls the freestream angle and thus AoA.

                              But I would say elevator and airspeed control AoA.

                              Comment


                              • #60
                                Originally posted by BoeingBobby View Post
                                I am sure glad I never had any of the three of you as F/O's.
                                I can monitor the transponder interrogation light as good as anyone.
                                Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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